Wear plate for a centrifugal pump

ABSTRACT

A wear plate for use in a centrifugal pump is structured with at least one cutting element positioned at the inner bore of the wear plate, the cutting element or elements being positioned to impact the cutting edge of the vanes of an impeller and oriented in a direction relative to the rotation of the impeller so that the wear plate cutting element or elements can capture the solids in a processed fluid and hold them in place until the solids can be cut by the impeller vane or vanes, the wear plate cutting elements further being structured to be self-sharpening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming priority toprovisional patent application Ser. No. 60/967,440 filed Sep. 4, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to centrifugal pumps, and relates specifically toa wear plate for a centrifugal pump having an inner bore edge structuredfor cutting solids.

2. Description of Related Art

Centrifugal pumps are structured with a pump casing in which an impelleris positioned for rotation. To maximize pump efficiency, the impeller ispositioned in close proximity to the pump casing inner surface toprovide minimal tolerances between the impeller and the pump casing.When such pumps are used to process fluids with a solids content, thesolids tend to erode or wear the inner surface of the pump casing,thereby leading to reduced pump efficiencies.

It is known in the pump industry to position a wear plate between theimpeller and the inner surface of the pump casing so that the wear plateis subjected to the erosive effect of the solids. The wear plate canthen be easily replaced when worn, rather than attempting to effect arepair or replacement of the pump casing. Certain types of centrifugalpumps are also configured with means for adjusting the position of thewear plate toward the impeller to decrease the gap therebetween as thewear plate becomes eroded.

When centrifugal pumps having wear plates are used to processsolids-entrained fluids, especially those containing stringy solids, thesolids can become lodged around the smooth inner bore of the wear plate.The stringy solids tend to be pushed and rolled by the edge of theimpeller without being cut. The accumulated solids then begin to causeexcessive wear between the impeller and the wear plate and the gapbetween the impeller and wear plate increases, thereby reducing pumpefficiency and allowing recirculation of fluid within the impeller.

In recognition of the deleterious effects that solids have on the pumpcasing, it is known to provide a wear plate that is configured andpositioned relative to the impeller to dislodge and direct solids awayfrom the inlet opening or impeller. Examples of such wear plate designsare disclosed in U.S. Pat. No. 6,139,260 to Arbeus and U.S. Pat. No.6,464,454 to Kotkaniemi. The wear plates of those inventions provide foran increased space between the wear plate and impeller, but theincreased space has the resulting effect of reducing pump efficiencies.

U.S. Pat. No. 7,037,069 to Arnold further discloses a wear plate for usein a centrifugal pump employing a single vane spiral-type impeller wherethe wear surface of the wear plate is provided with flow interrupters inthe form of notches and recesses that are perpendicular to the axis orrotation, and/or that extend in a direction opposite to the direction ofrotation of the impeller. The notches and recesses are provided tointerrupt the flow of fluid along the vane of the impeller and todislodge and clean solids from the impeller to move the solids towardthe volute of the pump for discharge. The flow interrupters arepositioned on the wear plate to remove solids from the impeller vane;however, they do not provide cutting or chopping of the solids.

It is further known in chopper type centrifugal pumps to provide chopperplates with cutter bars or cutting elements that span the eye of theimpeller to effect cutting of solids at the eye of the impeller. Suchcutter bar arrangements can prove beneficial to effecting the reductionand processing of solids, but also may. result in solids, particularlystringy solids, from accumulating at the eye of the impeller.

Thus, it would be advantageous to provide a means for cutting solids atthe cutting edge of an impeller in centrifugal pumps that processsolids-containing fluids, and to provide such means in a wear plate thatcan function to withstand the wear of processed solids.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a wear plate for use in acentrifugal pump is structured with at least one cutting element, butmost suitably a plurality of cutting elements, positioned at the innerbore of the wear plate. The cutting elements are positioned to impactthe impeller and are oriented in a direction relative to the rotation ofthe impeller so that the cutting elements can capture the solids andhold them in place until they can be cut by the impeller blade orblades.

Cutting elements on the wear plate of the present invention may bedistributed or spaced evenly or unevenly about the inner bore of thewear plate and may have any shape, size, dimension or configurationwhich will effectively cause cutting of solids at the inner bore of thewear plate. By facilitating the cutting of solids at the inner bore ofthe wear plate, the solids are more quickly reduced for processingrather than being simply flushed into the impeller, as is the purpose ofprior art wear plates. Additionally, the wear on the wear plate andimpeller are reduced so that the pump operation life is not decreased.

The cutting elements of the wear plate of the present invention arefurther configured with a wall, defined by the thickness of the wearplate and extending from the non-wear surface (i.e., that surfacepositioned away from the impeller) to the wear surface (i.e., thatsurface positioned adjacent the impellers, which is angled from thenon-wear surface to the wear surface of the wear plate, thereby imbuingthe cutting elements with a self-sharpening edge as the wear platewears.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be thebest mode for carrying out the present invention:

FIG. 1 is a perspective view in partial cutaway of a conventionalself-priming pump illustrating the relative positioning of the impellerand wear plate;

FIG. 2 is a perspective view in partial cutaway of a self-priming pumpillustrating the placement of the wear plate of the present invention;

FIG. 3 is a perspective view of a prior art wear plate having a smoothinner bore;

FIG. 4 is a perspective view of the wear plate of the present invention;

FIG. 5 is a perspective view of the wearplate and impeller as viewedfrom the wear surface of the wear plate;

FIG. 6 is a perspective view of the wear plate and impeller as viewedfrom the non-wear surface of the wear plate;

FIG. 7 is a plan view of the non-wear surface of the wear plate of thepresent invention;

FIG. 8 is an enlarged view of the cutting elements of the wear plate;

FIG. 9 is a view in cross section of the radius of the wear plate shownin FIG. 7, taken at line 9-9;

FIG. 10 is a perspective view of a prior art wear plate having a conicalshaped wear surface;

FIG. 11 is a perspective view of the prior art wear plate shown in FIG.10 illustrating the non-wear surface of the wear plate;

FIG. 12 is a plan view of an alternative embodiment of the wear plate ofthe present invention, the wear plate being generally frustoconical inshape;

FIG. 13 is a view in cross section of the wear plate shown in FIG. 12taken at line 13-13;

FIG. 14 is a perspective view of the non-wear surface of the wear plateshown in FIG. 12;

FIG. 15 is a perspective view of the wear plate of FIG. 12 shown inposition adjacent an impeller; and

FIG. 16 is a perspective view of the non-wear surface of the wear plateshown in FIG. 15 illustrating the interaction between the wear plate andimpeller.

DETAILED DESCRIPTION OF THE INVENTION

The wear plate of the present invention is adaptable for use in any typeof centrifugal pump which employs or can employ a wear plate positionedbetween the impeller and the pump casing or another adjacent structureof the pump. The present invention is described herein with respect to aself-priming pump by way of example only. Those of skill in the art willunderstand, based on the present disclosure, how to adapt the presentinvention to other types of centrifugal pumps.

FIG. 1 illustrates a conventional self-priming pump 10 which generallycomprises a pump casing 12, an inlet 14 and an outlet 16. The impeller18 is supported at the end of a bearing housing 20 and is connected to adrive shaft 22 for rotation. A clean out assembly 24 is axially alignedwith the impeller 18 and comprises an end cover 26 and a supporting ring28 that is spaced from the end cover 26 by a plurality of stanchions 30.The supporting ring 28 provides a means for attachment of a wear plate32, which positions the wear plate adjacent the impeller 18.

As best seen in FIG. 3, the prior art wear plate 32 is generallyconfigured as a flat plate having a thickness T extending between anon-wear surface 34 and an opposing wear surface 36 that is provided fororientation adjacent the impeller. The wear plate 32 is formed with aninner bore 38 that extends through the thickness of the flat plate andis provided with an inner circumferential edge 40 that surrounds theinner bore 38. In the prior art wear plate 32, the inner circumferentialedge is smooth. FIG. 3 also illustrates that-the wear plate 32 may besecured to the supporting ring 28 by bolts 44.

The wear plate 50 of the present invention is shown in FIGS. 2 and 4. InFIG. 2, where like parts of the pump are referred to by like referencenumerals, the wear plate 50 of the present invention is likewisesupported by a supporting ring 28 of a clean out assembly 24, and ispositioned adjacent the impeller 18.

FIG. 4 more clearly illustrates that the wear plate 50 of the presentinvention is formed, in this first embodiment, as a flat plate having athickness T extending between a non-wear surface 52 and an opposing wearsurface 54 that is provided for orientation adjacent an impeller. Thewear plate 50 is provided with means for attachment of the wear plate 50to the supporting ring 28 of the clean out assembly, such as bolts 56.

The wear plate 50 has an inner bore 58 formed through the center of thewear plate 50 and the inner bore 58 is formed with an innercircumferential edge 60. The inner circumferential edge 60 of the wearplate 50 is formed with at least one or, as shown here, a plurality ofcutting elements 62.

As illustrated in FIGS. 5 and 6, the cutting elements 62 are positionedto interact with the blade 66 or blades of the impeller 18 to produce acutting action at the inner circumferential edge 60 of the wear plate50. The cutting action of solids at the inner bore 58 of the wear plate50 assures that solids, particularly stringy materials, are processed toa smaller and/or more suitable form for movement by and through theimpeller 18.

As best seen in FIG. 7, the cutting elements 62 are generally producedby forming notches 70 in the inner circumferential edge 60 of the innerbore 58. The notches extend from the inner circumferential edge 60toward the outer edge 74 of the wear plate 50. Two adjacently-formednotches 70 produce a tooth 72. As illustrated in FIG. 7, there may bemore than one tooth 72 formed at the inner bore 58; however, a singletooth 72 may be formed in the inner bore 58. Further, as illustrated inFIG. 7, the plurality of teeth 72 may be spaced evenly about the innercircumferential edge 60. However, alternatively, the cutting elements 62may be spaced unevenly about the inner circumferential edge 60.

The notches 70 formed in the inner circumferential edge 60 arepreferably formed at a tangential angle to the inner circumferentialedge 60 such that a center line 76 (FIG. 7) of the notch 70 extends inthe direction of rotation of the impeller, as shown in FIG. 5. The angleof the notches 70 facilitates the capture of solids material in thenotch to enable cutting by the blade or blades 66 of the impeller 18.

As further illustrated in FIGS. 7-9, the notches 70 and teeth 72 areformed with a wall surface 80 that is defined by the thickness betweenthe wear surface 54 and the oppositely-facing non-wear surface 52 of thewear plate 50. The notches 70 are formed by cutting or machining throughthe thickness of the wear plate 50 at an angle to a plane 82, formedthrough the thickness of the wear plate 50, that is perpendicular to theplanes of the wear surface 54 and non-wear surface 52 of the wear plate50. That is, the angle A of the wall 80 is directed toward the center 84(FIG. 7) of the wear plate 50 in a direction extending from the non-wearsurface 52 to the wear surface 54 of the wear plate 50. Notably, thecenter 84 of the wear plate 50, when positioned in a pump, is co-axialwith the rotational axis of the impeller.

As best seen in FIG. 8, the angle A of the wall 80 of the notches 70produces a tooth 72 having an edge 86 formed by the wear surface 54which is greater than an edge 88 formed by the non-wear surface 52 ofthe wear plate 50. Consequently, the cutting elements 62 or teeth 72 ofthe wear plate 50 are self-sharpening as the wear plate 50 becomes wornby its interaction with the impeller (it being understood in the artthat the wear plate 50 is axially adjusted toward the impeller from timeto time as the wear plate 50 becomes worn).

The wear plate 50 described thus far, which is in the form of a flatplate, is suitable for use in smaller sizes, and certain types, ofcentrifugal pumps. In larger sizes or different types of centrifugalpumps, the wear plate may be formed in a generally frustoconical shape.FIGS. 10 and 11 again illustrate a frustoconical wear plate 90 that isknown in the prior art. The wear plate 90 has an inner bore 92 with asmooth inner circumferential edge 94. FIG. 10 illustrates the wearsurface 96 of the frustoconical wear plate 90 and FIG. 11 illustratesthe non-wear surface 98.

FIGS. 12-14 illustrate a frustoconically-shaped embodiment of the wearplate 100 of the present invention where the inner bore 102 has an innercircumferential edge 104 that is formed with at least one cuttingelement 106, or a plurality of cutting elements 106 as shown. FIG. 12illustrates the wear surface 108 of the wear plate 100 and FIG. 14illustrates the non-wear surface 110 of the wear plate 100. The cuttingelements 106 are formed in the manner previously described with respectto the flat plate embodiment illustrated in FIGS. 7-9, including theformation of the cutting elements to provide a self-sharpeningcapability.

FIG. 15 further illustrates the frustoconically-shaped wear plate 100 ofthe present invention where the wear surface 108 is positioned adjacentan impeller 120 of a larger size pump. FIG. 16 illustrates the non-wearsurface 110 of the wear plate 100 and illustrates the interaction of thecutting elements 106 with the blades 122 of the impeller 120. FIGS. 15and 16 illustrate the position and direction of the cutting elementsrelative to the direction of rotation of the impeller 120, as denoted byarrow 126. It can be appreciated from the view of FIG. 16 that thenotches 128 formed between the cutting elements 106 effectively trapsolids therein for cutting by the leading edge 130 of the impellerblades 122 as the impeller rotates.

The wear plate of the present invention can be adapted for use in anytype of centrifugal pump having an impeller, and especially a pump thatis used to process fluids which are laden with solids material. Thus,reference herein to specific details of the illustrated embodiments areby way of example only and not by way of limitation.

1. A wear plate for positioning adjacent to the impeller of a centrifugal pump, comprising: a plate having a wear surface, an opposing non-wear surface and a thickness defined therebetween; an inner bore formed centrally to said plate, said inner bore having an inner circumferential edge; at least one cutting element formed in said inner circumferential edge.
 2. The wear plate of claim 1 having a plurality of cutting elements formed about said inner circumferential edge.
 3. The wear plate of claim 1 wherein said plate is flat.
 4. The wear plate of claim 1 wherein said plate is frustoconically shaped.
 5. The wear plate of claim 2 wherein said cutting elements comprise notches formed in said inner circumferential edge, said notches having a centerline which is oriented in the direction of rotation of an impeller.
 6. The wear plate of claim 2 wherein said cutting elements are self-sharpening.
 7. The wear plate of claim 6 wherein said cutting elements have a wall that is formed at an angle to a perpendicular plane formed through said thickness of said plate.
 8. The wear plate of claims 7 wherein said wall is direct toward a center of said plate in a direction from said non-wear surface to said wear surface.
 9. A centrifugal pump, comprising: a pump casing; an impeller positioned within said pump casing and connected to a drive means for imparting rotation to said impeller; a wear plate positioned adjacent said impeller, said wear plate having a wear surface oriented toward said impeller, an opposing non-wear surface and a thickness defined therebetween, and further having an inner bore formed centrally to said plate, said inner bore having an inner circumferential edge with at least one cutting element formed in said inner circumferential edge.
 10. The centrifugal pump of claim 9 wherein said at least one cutting element further comprises a plurality of cutting elements.
 11. The centrifugal pump of claim 10 wherein said cutting elements comprise notches formed in said inner circumferential edge, said notches having a centerline which is oriented in the direction of rotation of an impeller.
 12. The centrifugal pump of claim 9 wherein said at least one cutting element is configured to be self-sharpening.
 13. The centrifugal pump of claim 9 wherein said at least one cutting element has a wall that is formed at an angle to a perpendicular plane formed through said thickness of said plate.
 14. The centrifugal pump of claim 13 wherein said wall of said at least one cutting element is directed toward a center of said plate in a direction from said non-wear surface to said wear surface. 